Shaping of the Earth's Surface
New NCERT Social Science | Academic Session 2026–27
The Earth's surface is continuously changing. Both internal forces operating inside the Earth and external forces acting on its surface play an important role in shaping the Earth's surface.
Internal forces originate from within the Earth. They can uplift, deform and create major landforms.
External forces act on the Earth's surface and gradually modify existing landforms.
These processes produce a wide range of landforms, from high mountain peaks and deep valleys to plateaus, plains, river valleys, deltas, coastal features and deep ocean floors.
The crust is the outermost and thinnest layer of the Earth.
The mantle lies below the crust and is much thicker. It contains very hot rocks and plays an important role in the movement of tectonic plates.
Tectonic plates are large slabs of solid rock that move very slowly. They generally move a few centimetres per year.
Major plates include the Pacific, Eurasian, African, North American, South American, Indo-Australian, and Antarctic Plates.
| Boundary | Movement | Main Features / Example |
|---|---|---|
| Convergent Boundary | Two plates move towards each other. | Continental plates may form fold mountains, such as the Himalayas. An oceanic plate colliding with a continental plate can cause volcanic activity and earthquakes. |
| Divergent Boundary | Two plates move away from each other. | Magma rises and forms new crust. Example: Mid-Atlantic Ridge. |
| Transform Boundary | Two plates slide past each other. | Crust is neither created nor destroyed. This movement mainly causes earthquakes. Example: San Andreas Fault in the United States. |
The Ring of Fire is an area around the Pacific Ocean. It has a high concentration of earthquakes and volcanoes. This is mainly due to the movement and interaction of tectonic plates.
India has experienced several major earthquakes in the past. Earthquakes can cause serious damage to human life, buildings, and the environment. Densely populated areas are especially vulnerable to earthquake damage.
In ancient times, earthquakes were known as “Bhukampa”, meaning the shaking of the Earth.
Varahamihira discussed earthquakes in the Brihatsamhita. He connected earthquakes with observations of wind, rain, clouds, animal behaviour, and planetary alignments.
The Mud Volcano at Baratang Island is a rare natural feature of India. It is located in the Andaman and Nicobar Islands. Unlike a fiery volcano, it produces mud due to natural underground gases and pressure.
Weathering is the process by which rocks on the Earth's surface break down into smaller pieces.
Rocks break into smaller pieces without changing their chemical composition.
Chemical reactions change the minerals present in rocks.
Plants, animals and microorganisms can contribute to the breakdown of rocks.
Erosion is the removal and wearing away of weathered material.
Transportation is the movement of sediments by water, wind, ice or gravity.
Deposition is the accumulation of transported sediments in a new location.
Glaciers are large masses of ice that move slowly under their own weight. They erode, transport and deposit materials.
A U-shaped valley is formed by glacial erosion.
A cirque is a bowl-shaped depression associated with glacial activity.
An arete is a sharp ridge between glacial valleys or cirques.
A hanging valley is a smaller glacial valley situated above the main valley.
A fjord is a deep, narrow sea inlet with steep sides formed from a glacial valley that has been flooded by seawater.
Moraines are deposits of rocks, soil and debris carried and deposited by glaciers.
| Type | Formation |
|---|---|
| Lateral Moraine | Forms along the sides of a glacier. |
| Terminal Moraine | Forms at the end of a glacier. |
| Medial Moraine | Forms in the middle when two glaciers meet. |
Wind erosion is especially important in dry and desert regions. Strong winds can carry loose sand, soil and dust.
Sand dunes are hills or ridges of sand formed by wind deposition.
| Type | Characteristics |
|---|---|
| Barchan | Crescent-shaped dunes. |
| Longitudinal | Long narrow ridges generally parallel to prevailing winds. |
| Star | Central peak with several arms. |
| Parabolic | Generally U-shaped and commonly associated with vegetation. |
In limestone regions, groundwater can dissolve rocks and create distinctive landforms known as karst landforms.
Karst topography develops mainly where soluble rocks such as limestone are dissolved by slightly acidic groundwater.
Fertile plains generally support dense settlements and intensive agriculture, whereas steep mountainous regions often have limited settlement and transport possibilities.
Understanding landforms is important for disaster preparedness and risk reduction. Areas with particular physical characteristics may be more vulnerable to earthquakes, landslides, avalanches, floods, volcanic eruptions, GLOFs and dust storms.
A landslide is the downslope movement of soil, rock or debris under the influence of gravity.
An avalanche is the sudden downward movement of snow and ice, sometimes mixed with rocks and debris, along a mountain slope.
A GLOF is a sudden release of water from a glacial lake because of the failure or overtopping of its natural dam.
A dust storm occurs when strong winds lift large quantities of loose, dry soil and fine particles into the atmosphere.
| Process | Important Landforms / Concepts |
|---|---|
| Glacial Erosion | U-shaped valley, Cirque, Arete, Hanging valley, Fjord |
| Glacial Deposition | Moraines |
| Types of Moraines | Lateral, Terminal, Medial |
| Wind Erosion | Yardangs, Ventifacts, Blowouts/Wind hollows, Desert pavements |
| Wind Deposition | Sand dunes |
| Types of Sand Dunes | Barchan, Longitudinal, Star, Parabolic |
| Karst | Limestone dissolution, caves, stalactites, stalagmites, pillars, sinkholes, underground rivers |